Implement macro-expand for subqueries

[kevinkdo]

If user types "subquerymySubqueryNameMy Subquery Definition", store that in this.state somehow. The word "subquery" is a keyword that indicates to us that the user is defining a subquery.

Then when they later type mySubqueryName, expand the word mySubqueryName into My Subquery Definition.

[mh291]

need to implement expansion when sending to back end

storing of subqueries works

[mh291]

need to test